1. Field of the Invention
The present invention relates to an apparatus for and a method of processing printing data of printed matter formed by a plurality of pages.
2. Description of the Background Art
In a step of preparing printed matter formed by a plurality of pages, a part of the plurality of pages is generally outputted as a single plate (or film), to be printed. In this case, the respective ones of the plurality of pages are formed independently of each other and composited with each other through the so-called assembling, to be outputted as a single plate.
FIG. 10 is adapted to illustrate first exemplary conventional composition processing. For convenience of illustration, it is assumed here that two pages are composited with each other.
Terminals 101 of a composition processor form printing data (hereinafter referred to as "page data") expressing the respective ones of a plurality of pages. The page data are in the following three data formats:
(1) "page description data" (e.g., "PDL" or "PDF") understandable by a programmer
(2) "intermediate data" (e.g., "run-length data") before bit-mapped development
(3) "raster data" (the so-called "bit-mapped data") which is the final output form
As shown in FIG. 10, the pages formed by an operator through the terminals 101 are generally expressed in page description data. Strictly, the operator forms an original expressed in page description data through the terminals 101 so that the original is split into the respective pages, while it is assumed that the pages are formed through the terminals 101, in order to simplify the illustration. An assembler 102 composites two pages which are expressed in page description data with each other. This assembler 102 merely composes a single plate from two pages, and the composed plate is expressed in page description data. Whether the two terminals 101 form pages respectively or either terminal 101 forms two pages, the respective pages are formed independently of each other, to be composited with each other through the assembler 102.
An interpreter 103 converts the composed plate to intermediate data, which in turn is further converted to raster data through a renderer 104. A recorder 105 outputs the plate expressed in the raster data, which can be outputted as printed matter, to complete the series of processing.
FIG. 11 is adapted to illustrate second exemplary conventional composition processing. In this example, two terminals 101 form pages in a page description data, which in turn are converted from intermediate data to raster data independently of each other through interpreters 103 and renderers 104 respectively. An assembler 102 composes a single plate from the two pages expressed in the raster data. A recorder 105 outputs the composed plate, which is expressed in raster data similarly to the aforementioned first conventional example.
The difference between the first and second conventional examples resides in that whether the pages are composited with each other in a page description data format or a raster data format, and the modes of the plates finally inputted in the recorders 105 are identical to each other.
However, the aforementioned conventional examples have the following problems respectively:
The first conventional example converts the data format of the plate after page composition, and hence the quantity of converted data is increased to require a long time for the processing. In this case, the composition processor may comprise a plurality of CPUs for performing the processing in a split manner, while it is difficult to split the composed plate formed by single data. If the pages forming the plate are prepared in different periods, further, the processing cannot be started until all pages are prepared, and hence the throughput of the overall unit cannot be improved. If the pages are formed in different data formats (when a certain terminal 101 forms a page of a raster data format, for example), further, the pages cannot be composited with each other unless the data formats thereof are equalized with each other.
On the other hand, the second conventional example composites the pages expressed in raster data with each other. In general, however, the information quantity of raster data is so large that a long time is required for compositing pages expressed in the raster data with each other, and hence it is difficult to improve the throughput as a result.
Further, pages once composited with each other may be corrected later. When page data are corrected, all processing must be performed again in both conventional examples, to remarkably reduce workability.